Skip Navigation Bar
NLM Technical Bulletin Header
Article Navigation Bar Table of Contents NLM Technical Bulletin Home Page Back Issues
 June 23, 2005 [posted] Identifier to be Added to MEDLINE®/PubMed® Data

drop cap letter for s tarting about July 2005, NLM will be including the identifier number in MEDLINE records, when that information appears in the original publication. For background information please see the International Committee of Medical Journal Editors (ICMJE) Web site for their editorial and updates on the topic of registering clinical trials before publication of the results. The ICMJE recommends that the clinical trial registration number be included at the end of the article's abstract.

The data will also appear in PubMed in the Secondary Source ID list in the Citation display, in the SI field of the MEDLINE tagged display, and in the DataBankList elements of the XML display. The general display format for the data is: an alphabetic label of followed by a slash and then an 11-digit alphanumeric string starting with NCT followed by eight numbers. An example in the Citation format display would be:

Secondary Source ID:


If there are multiple numbers mentioned in one journal article, all will be added to the MEDLINE record.

In PubMed, the data will be searchable using the [si] search tag; each of the pieces or the entire string is searchable, e.g.:

nct00000161 [si] [si] [si]

Use " [si]" to retrieve all citations to articles listing trial registration in regardless of which particular trial is involved.

By Sara Tybaert
MEDLARS Management Section
By Lou Wave S. Knecht
Bibliographic Services Division

black line separating article from citation

Tybaert S, Knecht LS. Identifier to be Added to MEDLINE®/PubMed® Data. NLM Tech Bull. 2005 May-Jun;(344):e13.


Article Navigation Bar NLM Technical Bulletin Home Page Back Issues Index Previous Page Next Article
U.S. National Library of Medicine, 8600 Rockville Pike, Bethesda, MD 20894
National Institutes of Health, Department of Health & Human Services
Copyright, Privacy, Accessibility, Freedom of Information Act (FOIA)
HHS Vulnerability Disclosure